295 research outputs found
Analysis-by-synthesis: Pedestrian tracking with crowd simulation models in a multi-camera video network
For tracking systems consisting of multiple cameras with overlapping field-of-views, homography-based approaches are widely adopted to significantly reduce occlusions among pedestrians by sharing information among multiple views. However, in these approaches, the usage of information under real-world coordinates is only at a preliminary level. Therefore, in this paper, a multi-camera tracking system with integrated crowd simulation is proposed in order to explore the possibility to make homography information more helpful. Two crowd simulators with different simulation strategies are used to investigate the influence of the simulation strategy on the final tracking performance. The performance is evaluated by multiple object tracking precision and accuracy (MOTP and MOTA) metrics, for all the camera views and the results obtained under real-world coordinates. The experimental results demonstrate that crowd simulators boost the tracking performance significantly, especially for crowded scenes with higher density. In addition, a more realistic simulation strategy helps to further improve the overall tracking result
Geometry-Based Multiple Camera Head Detection in Dense Crowds
This paper addresses the problem of head detection in crowded environments.
Our detection is based entirely on the geometric consistency across cameras
with overlapping fields of view, and no additional learning process is
required. We propose a fully unsupervised method for inferring scene and camera
geometry, in contrast to existing algorithms which require specific calibration
procedures. Moreover, we avoid relying on the presence of body parts other than
heads or on background subtraction, which have limited effectiveness under
heavy clutter. We cast the head detection problem as a stereo MRF-based
optimization of a dense pedestrian height map, and we introduce a constraint
which aligns the height gradient according to the vertical vanishing point
direction. We validate the method in an outdoor setting with varying pedestrian
density levels. With only three views, our approach is able to detect
simultaneously tens of heavily occluded pedestrians across a large, homogeneous
area.Comment: Proceedings of the 28th British Machine Vision Conference (BMVC) -
5th Activity Monitoring by Multiple Distributed Sensing Workshop, 201
Single Image Human Proxemics Estimation for Visual Social Distancing
In this work, we address the problem of estimating the so-called "Social
Distancing" given a single uncalibrated image in unconstrained scenarios. Our
approach proposes a semi-automatic solution to approximate the homography
matrix between the scene ground and image plane. With the estimated homography,
we then leverage an off-the-shelf pose detector to detect body poses on the
image and to reason upon their inter-personal distances using the length of
their body-parts. Inter-personal distances are further locally inspected to
detect possible violations of the social distancing rules. We validate our
proposed method quantitatively and qualitatively against baselines on public
domain datasets for which we provided groundtruth on inter-personal distances.
Besides, we demonstrate the application of our method deployed in a real
testing scenario where statistics on the inter-personal distances are currently
used to improve the safety in a critical environment.Comment: Paper accepted at WACV 2021 conferenc
Análise de multidões usando coerência de vizinhança local
Large numbers of crowd analysis methods using computer vision have been developed in the past years. This dissertation presents an approach to explore characteristics inherent to human crowds – proxemics, and neighborhood relationship – with the purpose of extracting crowd features and using them for crowd flow estimation and anomaly detection and localization. Given the optical flow produced by any method, the proposed approach compares the similarity of each flow vector and its neighborhood using the Mahalanobis distance, which can be obtained in an efficient manner using integral images. This similarity value is then used either to filter the original optical flow or to extract features that describe the crowd behavior in different resolutions, depending on the radius of the personal space selected in the analysis. To show that the extracted features are indeed relevant, we tested several classifiers in the context of abnormality detection. More precisely, we used Recurrent Neural Networks, Dense Neural Networks, Support Vector Machines, Random Forest and Extremely Random Trees. The two developed approaches (crowd flow estimation and abnormality detection) were tested on publicly available datasets involving human crowded scenarios and compared with state-of-the-art methods.MĂ©todos para análise de ambientes de multidões sĂŁo amplamente desenvolvidos na área de visĂŁo computacional. Esta tese apresenta uma abordagem para explorar caracterĂsticas inerentes Ă s multidões humanas - comunicação proxĂŞmica e relações de vizinhança - para extrair caracterĂsticas de multidões e usá-las para estimativa de fluxo de multidões e detecção e localização de anomalias. Dado o fluxo Ăłptico produzido por qualquer mĂ©todo, a abordagem proposta compara a similaridade de cada vetor de fluxo e sua vizinhança usando a distância de Mahalanobis, que pode ser obtida de maneira eficiente usando imagens integrais. Esse valor de similaridade Ă© entĂŁo utilizado para filtrar o fluxo Ăłptico original ou para extrair informações que descrevem o comportamento da multidĂŁo em diferentes resoluções, dependendo do raio do espaço pessoal selecionado na análise. Para mostrar que as caracterĂsticas sĂŁo realmente relevantes, testamos vários classificadores no contexto da detecção de anormalidades. Mais precisamente, usamos redes neurais recorrentes, redes neurais densas, máquinas de vetores de suporte, floresta aleatĂłria e árvores extremamente aleatĂłrias. As duas abordagens desenvolvidas (estimativa do fluxo de multidões e detecção de anormalidades) foram testadas em conjuntos de dados pĂşblicos, envolvendo cenários de multidões humanas e comparados com mĂ©todos estado-da-arte
3D Random Occlusion and Multi-Layer Projection for Deep Multi-Camera Pedestrian Localization
Although deep-learning based methods for monocular pedestrian detection have
made great progress, they are still vulnerable to heavy occlusions. Using
multi-view information fusion is a potential solution but has limited
applications, due to the lack of annotated training samples in existing
multi-view datasets, which increases the risk of overfitting. To address this
problem, a data augmentation method is proposed to randomly generate 3D
cylinder occlusions, on the ground plane, which are of the average size of
pedestrians and projected to multiple views, to relieve the impact of
overfitting in the training. Moreover, the feature map of each view is
projected to multiple parallel planes at different heights, by using
homographies, which allows the CNNs to fully utilize the features across the
height of each pedestrian to infer the locations of pedestrians on the ground
plane. The proposed 3DROM method has a greatly improved performance in
comparison with the state-of-the-art deep-learning based methods for multi-view
pedestrian detection
A Social Distance Estimation and Crowd Monitoring System for Surveillance Cameras
Social distancing is crucial to restrain the spread of diseases such as COVID-19, but complete adherence to safety guidelines is not guaranteed. Monitoring social distancing through mass surveillance is paramount to develop appropriate mitigation plans and exit strategies. Nevertheless, it is a labor-intensive task that is prone to human error and tainted with plausible breaches of privacy. This paper presents a privacy-preserving adaptive social distance estimation and crowd monitoring solution for camera surveillance systems. We develop a novel person localization strategy through pose estimation, build a privacy-preserving adaptive smoothing and tracking model to mitigate occlusions and noisy/missing measurements, compute inter-personal distances in the real-world coordinates, detect social distance infractions, and identify overcrowded regions in a scene. Performance evaluation is carried out by testing the system's ability in person detection, localization, density estimation, anomaly recognition, and high-risk areas identification. We compare the proposed system to the latest techniques and examine the performance gain delivered by the localization and smoothing/tracking algorithms. Experimental results indicate a considerable improvement, across different metrics, when utilizing the developed system. In addition, they show its potential and functionality for applications other than social distancing.Peer reviewe
- …